1. Field of the Invention
The present invention relates to a composition and method for treating composting material used for cultivating edible fungi such as mushrooms to significantly reduce the malodorous gases normally associated therewith, retain water in the fibrous component of the compost composition, and enhance the nutritional quality of the edible fungi without detrimentally affecting crop yield.
2. Description of Related Art
The composting of animal waste to create a suitable organic substrate in which to cultivate mycelia of edible fungi has long been the accepted practice. The process, on which there are several variations, is generally one of aerobic biodegradation, i.e., fermentation, and comprises the use of horse manure and poultry manure; straw or other carbohydrate-rich substances essentially containing cellulose, hemicellulose, and lignin; nitrogen-rich nutrients, e.g., cotton seed, sunflower seed, seed meals, brewer's grains, and urea; and inorganic conditioners, e.g., lime and gypsum. Broadly speaking, composting involves the fermentation of straw and animal manure over a period of approximately one month, with periodic turning and wetting to assure proper biological activity.
The straw or cellulosic material is wet with water prior to mixing to provide moisture to the fermenting microorganisms during the fermentation process. Such wetting usually requires copious amounts of water due to the waxy nature of the straw's surface. The excess water runs off into a catch basin, carrying with it residual manure solubles and suspended organic matter, causing an accumulation of odor-causing agents in the catch basin.
Mushroom cultivation has been an activity carried out in relatively remote rural areas. However, as these formerly remote locations have become more densely populated because of urbanization and because increased commercial demand for the produce has caused growers to greatly enlarge their processing and growing facilities, government entities and concerned neighbors have brought attention to the odors and runoff associated with the traditional methods commonly practiced in this agribusiness.
The odors are largely caused by volatile sulfur compounds released by the microbial action during fermentation. These include hydrogen sulfide, methyl mercaptan, dimethyl sulfide, carbonyl sulfide, carbon disulfide, and dimethyl trisulfide. Ammonia, and traces of acetone, butanone, 3-methylbutanone, and 2-pentanone, have also been identified in the gas emissions from compost stacks (Derikx et al. (1990) "Odorous Sulfur Compounds Emitted During Production of Compost Used As A Substrate In Mushroom Cultivation", Applied and Environmental Microbiology 56:176-180). It is feared that the water runoff may leach into the ground water and cause pollution of drinking water for livestock and humans alike.
Odor control in the field of animal waste composting for mushroom cultivation has been addressed from several points of view. Miller and Macauley (1989) "Substrate Usage and Odours In Mushroom Composting", Australian Journal of Experimental Agriculture, 29:119-124, report that the odor problems are directly associated with the compost formulations, and that by adjusting the activator (nitrogen-rich nutrient) constituent in relation to the total dry weight, one may achieve reduced odor emissions. U.S. Pat. No. 3,345,152 teaches a method of deodorizing manure and human excreta by distilling the waste material at temperatures of 400.degree. F. and reintroducing the gaseous effluent--water removed--into the waste stream to be "bonded" thereto. The resulting odor is that of a tobacco- or barbeque-like smell. Whereas this method changes the odor to one less offensive, the heat of distillation would destroy the microorganisms required for aerobic fermentation.
Methods of mushroom growth activation have been reported in the patent literature and in scholarly journals. For example, U.S. Pat. No. 4,420,319 teaches methods of effecting greater yield in shortened periods by employing a multistage process of the introduction of a manufactured mushroom spawn activator in combination with a delayed-release nutrient particle. U.S. Pat. No. 4,990,173 teaches a nutrient supplement for enhancing the growth of mushrooms comprising a protein-rich material coated with a hydrophilic carbohydrate. U.S. Pat. No. 3,560,190 teaches the use of dry, friable, granular nutrient supplement comprising a blend of cottonseed meal, cottonseed oil, and a hardwood sawdust as an absorbent. The novelty of that teaching is evidenced by the increase in volume of the mushroom harvest. U.S. Pat. No. 4,370,159 further teaches an improved nutrient growth-stimulating additive for mushroom compost which comprises the mixing of materials including soy and/or cottonseed oil with soy protein concentrate, calcium caseinate, sodium acetate, and lecithin. Successful growth stimulation was achieved. U.S. Pat. No. 5,186,731 claims a method of cultivating mushrooms comprising mixing mushroom spawn with compost and an amount of supplement to enhance the yield of fruiting bodies, said supplement being a calcium and/or amine salt of an aliphatic, alicyclic or heterocyclic carboxylic acid. It further teaches that said acids may be mono- or dibasic, saturated or unsaturated, and have up to 20 carbon atoms. The amine salts of that invention comprise ethylamine, diethylamine, triethylamine, triethanolamine or ethylenediamine.